Title

Author

Degree Type

Dissertation

Date of Award

2012

Degree Name

Doctor of Philosophy

Department

Animal Science

First Advisor

Nicholas K. Gabler

Abstract

Lipopolysaccharide (LPS) and the inflammation associated with its stimulation of the innate immune responses can have major implications for human and animal health and production. This dissertation research goal was to further understand dietary modulation of intestinal LPS permeability and LPS associated inflammation. Additionally, we sort to examine LPS detoxification and the relationship LPS has with swine health and feed efficiency.

High caloric and high dietary fat increases the risk of endotoxemia which can result in a low grade inflammation, a predisposing factor for common metabolic diseases such as Type II diabetes and atherosclerosis. However, little is known about the effect of dietary oil fatty acid composition on intestinal LPS permeability and postprandial endotoxemia. Therefore, we examined whether dietary oil composition differentially modulated intestinal LPS permeability and postprandial endotoxemia. Our in vivo and ex vivo research using pigs and isolated pig intestinal tissues indicated that a single administration of oils rich in long chain n-3 polyunsaturated fatty acids (PUFA), such as fish oil and cod liver oil, decreases LPS permeability and postprandial circulating LPS levels (P<0.05). Furthermore, oils rich in saturated fatty acids, such as coconut oil, augmented LPS permeability and postprandial endotoxemia (P<0.05). Mechanistically, this may be associated with the structure and function of cell membrane lipid raft microdomain structures.

Dietary long chain n-3 PUFA such as eicosapentaenoic acid (EPA) and docoasahexaenoic acid (DHA) have been shown to antagonize LPS signaling. Therefore, we examined the ability of dietary EPA and DHA to attenuate intestinal LPS permeability and lipid raft localization of key LPS signaling proteins. Long term dietary EPA and DHA supplementation to pigs enriched intestinal epithelial membrane with EPA and DHA (P<0.05). Phospholipid fatty acid composition of the lipid raft fractions also revealed enrichment of phosphatidyl ethanolamine and phosphatidyl serine with EPA and DHA. Mechanistically, membrane EPA and DHA enrichment decreased localization of LPS signaling proteins, TLR4 and CD14, into ileum and colon lipid raft microdomains. Collectively, this decreased ex vivo LPS permeability and circulating LPS concentrations (P<0.05). Interestingly, an acute systemic inflammatory challenge resulted in a decreased localization of TLR4 and CD14 into lipid rafts, which has the potential to desensitize the pigs to a subsequent immune challenge otherwise known as LPS tolerance.

The ability of the maternal diet and prenatal nutrition to impact postnatal growth, development and health has received much attention in recent years. Knowing that DHA and EPA can regulate the innate immune response to an LPS challenge, we wanted to study if maternal n-3 PUFA supplementation of n-3 PUFA could modulate an acute inflammatory challenge in the offspring later in life. Sows and piglets received nutrition devoid or enriched with EPA and DHA during gestation and lactation or throughout life from gestation to ten weeks of age. The offspring was then challenged with LPS or saline to initiate an inflammatory response and buffy coats isolated 4 h post challenge. Interestingly, maternal n-3 PUFA supplementation attenuated the LPS induced inflammatory response in the offspring late in the nursery phase of growth (P<0.05). This was comparable to that of continuous n-3 PUFA supplementation. Both treatment groups exposed to DHA and EPA had a decreased febrile and serum TNF-alpha; cytokine response to LPS, buffy coat mRNA abundance of TNF-alpha;, IL-1beta; and IL-10 and the mRNA abundance of the LPS signaling proteins, TLR4, CD14 and Myd88, compared to control group (P<0.05).

Lastly, we used pig lines divergently selected for residual feed intake (RFI, with low RFI being more efficient compared to high RFI) to understand the relationship between intestinal barrier integrity, LPS and associated inflammation with pig feed efficiency. Our research indicates that HRFI pigs seem to be undergoing a greater level of basal inflammation contrary to pigs selected for LRFI. The LRFI pigs had a lower circulating endotoxin concentration, more robust intestinal and liver LPS detoxification and higher active anti-microbial enzymes including alkaline phosphatase and lysozyme (P<0.05). Furthermore, LRFI pigs had a reduced activity of the inflammatory biomarker enzyme myeloperoxidase (P<0.05). Altogether, LPS and low grade inflammation may partially explain the divergence in feed efficiency and RFI in grow-finisher pigs.